[anneal] Define Rust-level verification evidence

[joshlf]

Add anneal/docs/rust-verification.md as the next detailed design document below the verification-result model.

The document models Rust-level verification as an adequate reduction from an exact Rust claim to proof obligations, relative to the result's explicit TCB. This deliberately avoids requiring one canonical source model: source/model correspondence, translation validation, simulations, or other mechanisms are possible realizations of the same requirement.

The model treats weak obligations and unaccounted-for behavior as two manifestations of one adequacy failure, makes coverage semantic rather than syntactic, explains how adequate reductions compose across translation stages, and makes circular UB assumptions visible rather than allowing a successful model theorem to stand in for Rust-level evidence.

anneal/DESIGN.md and anneal/docs/verification-results.md gain only routing links to the new document.

This PR is stacked on #3701 because the verification-results document it elaborates has not yet merged. Both the conceptual model and the prose articulation were refined using model-refinement at joshlf/skills@7aa3d651bc7abfeb7403d6ccfe962fa11cc4b049 before publication.

Authored by an AI agent acting on Josh Liebow-Feeser's behalf.

[chatgpt-codex-connector]

You have reached your Codex usage limits for code reviews. You can see your limits in the Codex usage dashboard.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.90%. Comparing base (06a1f71) to head (d3bbfb1).

Additional details and impacted files

@@                     Coverage Diff                      @@
##           anneal-verification-results    #3702   +/-   ##
============================================================
  Coverage                        91.90%   91.90%           
============================================================
  Files                               20       20           
  Lines                             6175     6175           
============================================================
  Hits                              5675     5675           
  Misses                             500      500           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.